High power vacuum fuse apparatus

ABSTRACT

Vacuum fuse apparatus includes a pair of arcing electrode assemblies in the form of an interleaved array. A fusible element is connected between members of each electrode assembly. When the current carrying capacity of the fusible member is exceeded it fails and an arc is struck between parallel gaps of the interleaved rod array. Arc is extinguished upon occurrence of a zero value of current through fuse device.

[451 Apr. 10, 1973 United States Patent 91 v Keenan [541 HIGH POWER VACUUM FUSE m am &A :lP S am MA r 1 S w m P P A [75] Inventor; James J. Keenan, Schenectad N.Y. [7.31 Assignee: General ....3l3/325 X ..........337/33 ....313/233 X 2,526,370 10/1950 Kott..;........ 3,153,128 10/1964 Carothers.. mean-c Cmmpany, 3,509,406 4/1970 Schenectady, NY.

" Mai-.20, 1972 I Primary Examiner-John K. Corbin 22 Filedr 21 Appl.No.:235,946

AttorneyJ0hn F. Ahern wA a mm m he mm trode assemblies in the form of an i fu [52] US. Cl. .................3l3/233; 313/217, 313/267,

sible element is connected between members of each electrode assembly. When the curre nt carrying capacity of the fusible member is exceeded it fails and an arc is struck between parallel gaps of the interleaved rod array. Arc is extinguished upon occurrence of a zero value of current through fuse deviceQ m 9 3 a h% 11. 0 95 Huey m 1 7 235 .l 3 l 0 5 "2 m m WW7 6 m3 m3 rH 8 a tm MF 111 8 55 p 17 Claims, 5 Drawing Figures PATENTEU 1 01975 SHEEI 2 UF 4 HIGH POWER VACUUM FUSE APPARATUS BACKGROUND OF THE INVENTION The present invention relates to high current vacuum fuse apparatus adapted to operate at kilovolt ranges. More particularly, the invention relates to such apparatus as uses a fusible element in an evacuated chamber in conjunction with a pair of arc electrode assemblies having broad area for the sustenance of a very high value of arcing current without damaging the arc electrode structure thereof.

As is well known in the art, a vacuum fuse operates utilizing a fusible element in an evacuated chamber. Upon exceeding of the rated current for the fusible element, the element fuses and disintegrates causing a current-carrying are between the supports thereof, which is extinguished upon the occurrence of an instantaneous zero value of alternating current. In the vacuum environmentthe arc is not restruck upon the occurrence of the next half cycle. 7

As the requirements for fusing alternating currents of increasing values have increased, greater and greater stress has been placed upon the conventional structure. Conventional fuses, i.e., fusible element in air, gas, or oil, are less-and less capable of interrupting very high fault currents without destructive incidents. Previously, vacuum fuses have been only very low voltage and current devices and have not been applicable to high power circuits. To-date, high power fuses are prohibitively large and expensive, and must be made even larger as power requirements increase.

Accordingly, it is an object of the present invention to provide high voltage, high current vacuum fuse apparatus.

Another object of the present invention is to provide vacuum fuse apparatus which may interrupt high currents and sustain very high arcing current values without'damage to the arcing members therein.

Still another object of the present invention is to provide vacuum fuse apparatus which, upon a single operation, uses a fusible element leaving a device which may further be operated as a triggerable gap device without further replacement of parts.

BRIEF DESCRIPTION OF THE INVENTION In accord with one embodiment of the present invention, I provide an evacuated vacuum envelope containing a pair of arc electrode assemblies, each of which includes a baseplate and a plurality of parallel rod-like arc electrode members disposed'with respect to and intersecting the baseplate'in perpendicular relation and a substantially circular configuration. The two arc electrode assemblies are interleaved with one another to provide a circular rod array which provides a plurality of parallel arcing gaps therebetween. A fusible member is disposed about the periphery of the rod gap array portion of said interleaved arc electrode structures and is connected electrically and mechanically to at least one of the rod-like members of each electrode array. It may be connected to more than one and, in the limit, it is connected to each of the individual rod-like members of each array thus providing a set of parallel fusible members with a composite current carrying capacity. When a current in excess of the rated current carrying capacity is impressed upon the structure, the fusible member fails by melting, disintegrating or exploding and the arcing current is spread over the broad area of the plurality of arcing gaps between the rod-like members and is carried thereby until the occurrence of a zero value of the alternating applied current, at which the arc is extinguished.

The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof may best be understood with reference to the following description taken in 7 connection with the appended drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-sectional view of a vacuum fuse constructed in accord with the present invention.

FIG. 2 is a schematic plan view taken through the center of the device of FIG. 1.

FIG. 3 is a schematic, vertical, cross-sectional view of another embodiment of the invention alternative to the embodiment of FIG. 1.

FIG. 4 is still another schematic vertical cross-sectional view of an alternative embodiment of the invention similar to the device of FIG. 1, and

FIG. 5 is still another schematic, vertical, cross-sectional view of yet another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a vacuum fuse constructed in accord with the present invention, is represented generally at 10. Fuse 10 includes an evacuable envelope 11 which comprises an insulating sidewall member 12 hermetically sealed in ceramic-to-metal seal to a pair of arc-electrode assemblies 13 and 14 by means of ceramic-tometal seals 15 and 16, respectively. Upper arc-electrode assembly 13 includes a base member 17 and a plurality of rod-like arc-electrode members 18 normally disposed thereto and downwardly depending into the volume of envelope 11. As may readily be seen from the sketch of FIG. 2, arc-electrodes 18 are arranged in a generally circular pattern along base member 17. Arc-electrode assembly 14 includes a base member 19 and a plurality of upwardly depending, parallel, rod-like electrode members 20 which are normal thereto and similarly arranged in a circular pattern intimately electrically and mechanically affixed to the base member in a circular configuration. Arc-electrode assemblies 13 and 14 are disposed so that the respective rod-like members 18 and 20 are interleaved alternately between one another to form a circular array of rod-like members and define a plurality of electrically parallel inter-electrode gaps between the arc-electrode assemblies 13 and 14, respectively, defining a very broad area for arcing therebetween so as to conduct a very high current at a very low current density.

' switch. Y

length and define in the region of overlapping, an interaction gap, within which the actual operation of the device occurs. The interaction gap is surrounded by a shield member 21 which may, for example, as illustrated, have the form of a doubly truncated cylinder supported on support member 23 which is affixed to seal member 23 and sealed to the cylindrical sidewall member 12."To further preserve the insulating integrity of insulating sidewall member 12 and to further protect the integrity and durability of seals 15 and16, a pair of end shields which overlap the respective ends'of cylindrical shield 21 are providedin the form of shield members 24 and 25 which are affixed. to endwall members 17 and 19 respectively and depend inwardly into the interaction gap. Means are provided for connecting the fuse 10 in circuit with an electric circuit which is sought to be protected or with specific electric apparatus likewise sought to be protected, in the form of terminals 26 and 28, which are in intimate electrical and space, the arc spreads more evenly. Therefore, this embodiment is preferred and is illustratedin all figures, although it is not necessary to the practice of the invention.

For purposes of convenience of assembly, the fusibl element is preferably connected substantially adjacentto the inwardly depending end of one of the arrays of parallel rods. Thus, for example, preferably the fusible element may be located at a distance from the inwardly depending end within approximately one or twotimes the diameter of an individual rod, should rods be used, or one or two times the minimum dimension of any other configuration of rod-like member utilized.

mechanical contact with arc electrode assemblies 13 and 14, respectively. As is shown for convenience sake,

' Pat. No. 3,679,474, assigned to the present assignee and incorporated hereinby reference thereto. ln ac- The vacuum nature of the device in accord with the invention requires the freedom from gas and gasemitting materials for anypart of the device which is exposed to a high current arc during the extinction of a fault current carrying arc. Thus, the arc-electrode assemblies l3 and 14, including rod-like members 18 and 20, as well' as base members 17 and 19 and all of the shield members, should be essentially gas-free. Whilein devices such as vacuum switches which are normally cord with the present invention, the device described hereinbefore, which is essentially an open gap vacuum device which is evacuat'edfto a'vacuum of at least approximately 10" torr, but preferably to approximately at least 10" torr. This electrodestructure is then utilized as support means for a fusible element and as means to nondestructively sustain and extinguish. a fault currentcarc which is struck thereacross when the fusible elementv fails. Thus, my invention creates a vacuum fuse which is capable of dissipating theenergy of a fuse-initiated arc .in the manner .of a vacuum Vacuum fuse 10 is completed by the suspension of a utilized to carry very high currents for a very great length of time a greater freedom is required as is set forth in US. Pat. No. 2,975,256 to Lee et al, in devices of .the present invention, it is necessary that the freedom from gas and gas-forming constituents need satisfy the less strict criterion that the working vacuum, for example, at least approximately 10" torr and preferably at least approximately 10' 'torr, not be substantially altered when an arcing current of approximately 30 kiloamperes is carried between the arc'electrode assemblies 13 and 14 for a period of one full cycle of the powercurrent frequencyas, for example,

60 Hz. This is substantially a less'severe test then proposed, for example,'for butt-type vacuum switch electrodes wherein exceedinglyhigh current densities fusible element '30 between at least one each of rods 18 and 20. As illustrated, fusible element 30 is wound about the interleaved array of 'rods 18 and 20 and contacts each of rods 18, 20. Fusible element 30 may have any convenient physical structure.' For example, it may be a wire with a circular or elliptical cross-section; it may be a ribbon-with a rectangular cross-section; it

' may be a laminated structureor-any of the fusible structures suitable for such applicationsand generally known in. the art. Element 30is positioned about the periphery of the arc electrode. rods 18, 20 and mechanically and electrically affixed thereto, as by lightlyspot-welding at a point tangent to the exterior of cylindrical rods or at an appropriate similar place on other configurations of individual arc electrode members. As mentioned hereinbefore, fusible element 30 may connect only one each'of rod-likemembers 18, 20. It is-readily apparent, however, that the'greater the number of rods that are connected, the greater will be the current (steady-state) carrying, or rated, capacity of the fuse. Additionally, if the fusible element fails simultaneously in. all lateralportions of the interaction are concentrated upon the arc electrodes. r

, Due to the broad areaofthe arc-electrodes herein and due to the structure which, according to, the-aforementioned Rich application, causes the elimination of J X'Bforces which tend to constrict current-carrying paths and form destructive anode spots, the rod-like electrode members 18,20 of the device of the present invention may utilize commercial OFHC copper, as'is set forth in the aforementioned Rich application or, al-

ternatively, -may utilize maraging steels or other hardenable'steels such as transformation hardened,

precipitation hardened, and other classes of'steels which have a relatively high hardness and a reasonable ductilityso as to gain the advantages of the ideal hardnessductility" combinations to provide a hard electrode structure which is resilient enough to withstand material which is sufficiently free of gases such that the volatilization thereof during fusing does notrelease a sufficient amount of gas into the volume of the vacuum fuse device to deleteriously substantially affect the vacuum thereof. This degree of purity may be described as having the same purity as is set forth in the aforementioned Lee et al patent, briefly paraphrased as a purity of less than one part in of gases or gasforming materials. Chemically, the fusible element may conveniently be copper or an alloy thereof, nickel and alloys thereof, or any material suitable forfusing applications and similarly adaptable for the removal of gases therefrom in accord with its use in vacuum are devices.

The fusible material must be bakeable and therefore must be substantially refractory, i.e., it rnust'have'a melting point in excess of 400C and preferably in excess of 600C to withstand vacuum bakeout without any deleterious action thereupon. In addition to copper and nickel, molybdenum, tungsten, silver, iron, are all suitable materials,-it being understood that the crosssectional dimension thereof 'ch'osenmust be consistent with the number of parallel fuse paths and with the current rating so as to cause fusing at the desire current.

In operation, a typical device decribed for purposes of completeness only, but not in a limiting sense, is fabricated as indicated in FIG. 1. It should be understood, however, that although FIG. 1 illustrates a device having six rods in each arc-electrode assembly, this number is chosen for purposes of illustration to bring out the concept of the interleaved rod array and, therefore, is for purposes of illustration and does not constitute an ideal embodimenLAny number of rods may be utilized, a preferred number being three rods t ea t. 0? od 0t t r with ni he ev e while n re. vi ish d o-a t pe t r wh h may e.

for example, from 500-600;-C fora'timeof for exam- ;ple '5 to .24 hours. 'Altematively, the-devicemay be fabricated substantially as; illustrated before bakeout and. a .vauum .tip-Qff .tube zadded .to, connect with; 'a

vacuum pump for evacuation during bakeout. Y,

In oneusage; the fuse device is connected inseries rCil'Clllt relationship, for example, with the deviceor'cirt uitto beprotected, depending uponlthe usage. Typi- "cally,*a'set of electricalparametersfor the operationof devices in accord with the present-invention includes "operating at a rated voltage of kilovolts 'at a steadystatemaxinitim current of 200 amperesiRMSwith'no greater temperature'rise at terminals26and 28 then 65C above ambient. Upon fusing of 'tlie-fusible elements, (normally in response to an over'voltagetor transient phenomenon such as a lightning-strike) it is necessary that the devices in accord with the present invention be able to conduct approximately 12,000 amperes RMS symmetrical component (30,000 amperes peak) for a time up to one full cycle of the power alternating frequency before extinction at a current zero. This has been accomplished in accord with the present invention utilizing one device wherein the rod structure are electrode assemblies were fabricated from Vascomax 3 00 CVM maraging steel obtainable from Vanadium Alloy Steel Co., Latrobe, Pa., with rods of 54 inch in diameter and 4% inches in length, enclosed in a 6 inch long vacuum chamber having an interior dimension of 2% inches. Each of the arc electrodes apparatus utilized three such rods for a total of six rods ina circular array. The fusible element utilized comprised a 0.02 inch OFI-IC copper wire crimped to the exterior periphery of rod electrode member. As mentioned hereinbefore, this device was designed to fail and fuse at a current substantially in excess of 200 amperes in a nominal 15 KV voltage rated circuit and operated successfully, clearing on current zero and failing to restrike.

FIG. 3 illustrates an alternative embodiment of the invention, wherein like numerals are utilized to identify like elements to the device illustrated in FIG. 1 of the drawing. In FIG. 3, vacuum fuse 10 is included within envelope l1 and contains arc electrode assemblies 13' and 14 having base members 17 and 19 respectively and rod electrode members 18 and 20 respectively, as in the device of FIG. 1. In the device of FIG. 1, a single fusible elementwas circumferentially wrapped around the individual rod-like members of the array of the interleaved arc electrode structures. In the device of FIG.

3, a pair of fusible elements 30 and 31 are located, each with the criteria set forth for the location of the individual fusible member 30 in FIG. 1. That is to say, each is located adjacent the approximate inwardly depending'end of one set of arc electrode arrays and preferably within a distance equivalent to one or two times the diameter of an individual rod electrode member from the inwardly depending end thereof. The use of two fusible elements, one about the inboard end of each rod array increases substantially the load current carrying capacity of the device by introducing an additional conduction path and thus there is advantage to having two independent fusible elements, as is illustrated herein.

*FIG.4 of the drawings illustrates yet another embodiment of the invention, which utilizes, in lieu of a single fusible'element as in FIG. 1 or two fusible elements as in FIG. 3, a single fusible element 32in the form of a spiral or helix which is wrapped laterally around the entire interaction space of the rod array which overlap and interleave with one another, thus further increasing the load current carrying capacity of this embodiment. The individual rod members are fastened, as by crimping, brazing, spot welding, or the like,'a't each point at which the t'us'ibleelement passes the periphery thereof to insure stability and good electrical and mechanical'contact thereto.

It has been found in-the devices constructed in accord with the present invention that, upon'th'e exceed- 1 ing ofthe rated currentthrough thefusible element and the! fusing 1 and ,destruction ,thereof, resulting in the establishmentof a high current discharge through the rodfigap arrayof the 'arc relectrode structures, that the fusible'element is substantially totally removed from device which hassubstantial"utility -In further accord j with'm'y invention, I provide means for causingfurther breakdowns of such devices after the initialfusi'ng by the-electrode structures.- and that'the rodgap array remaining constitutes a useful operative vacuum gap incorporating thereintomeans for injecting an electron ion plasmainto the interaction space'between the inter leaved rod-like electrode members to cause breakdown at any predeterminedtime under the appropriate'volt age conditions.- .1 V r r p One such means is illustrated in FIG. 5 wherein like membersof the device are represented by the same j to a trigger'anddeilead 45 which passes through an in- ,sulating'bushing 46f: I

In operation, the fusibleimember 30ris caused to fuse bly'the passage therethrough of a current in excessof the rated current to cause afr-rst arcingand the diffusion I of an electron ion plasma from the fused fusible I elementbetween the oppositely disposedarc'e'lectrode members 18 and 20. Afterthe occurrence of a first cur- :r'ent zeroand thesextinctionofr such arcing by collectionof the particles from the'fusible element upon exposed surfaces, the; device may then caused to operate to breakdown upon the 'injection of an ele'c:

.tron ion plasma by meansof trigger assembly 41JThis maysconveniently be done,,foriexample, by applying a connection of terminals 26 and 28 to analternating current'powe'r line. Upon the occurrence'of the. cycle iwherein electrode assembly-14th negative, the. voltage discussed with reference to the broad area arcing rod array electrode structureof the aforementionedRich application, the novel concept of a fusible elementin a vacuum arc envelope having a pair of interleaved broad area arcing electrode structures which both supportthe fusible element and sustain and extinguish, the fault current caused by the failure of the fusiblelelement, is not limited to incorporation with the Rich frod array structure. An'yjsuch structure which diffuses a current carrying arc of high value to a low'de nsity multi-path discharge to facilitate extinction of anA. C. high power are is within contemplation of the invention. Thus ,for

' example, fu'sible elements connected between at least I one each, and preferably all of the multi element arcf electrode structure of anyof US. Pat. No. 3,356,893 5 Lafferty;.U.S. Pat. No. 3,356,894 Lafferty; US. Pat.

No. 3,432,7l3 Lafferty; U.S.'Pat. No. 3,471,733, Rich;,U. S. Pat. No. 3,471,734 Rich; I J. S. Pat. No. 3,471,736- Rich; U.S. Pat. No. 3,509,404 Rich; U.S; Pa t Q NO. 3,509,405- Rich; and U.S. Pat. NO. 3,509,4 06

- Rich are within the contemplation and scope of the inandrods 20 or baseplate l9 and rods 18. Alternatively,

ventionL sq, also I are fusible elements connected between an portion of the pair of electrodes of the disclosed RichfRod Array Structure, as, for example, one or more fusible elements running from baseplate l7 tov baseplate '19 in FIG. 1. So also one or more'fusible', elements running between either of baseplate -l7- 'oneor more fusible elements may rujn' between one of the baseplates and noninterleavcd rods extending from the other baseplate or betweentwo such rods extending from opposite'baseplates. Thus, since it is a newconcept to utilize broad area vacuum gap type electrodes :todissipate an arc struck by failure of a fusible element in vacuum, theinvention is such as to embody all-such means to accomplish that result.

, By the foregoing, there have been described vacuum 'fuse devices having the unique abilitytofuse and protect'anelectric circuit'or electric apparatus by'provitL I ing mfi f td-interrupts circuit or short circuit the same uponjthe passage 'ofa current in excess of-a ,45 positive pulse of the order of "1,000 volts to trigger anode lead f'while'a voltage of 15 kilovo'lts A; C. is applied betweenarc electrode assemblieslS and by -acro'ss; gap 43 causes-thebreakdown, thereof and the -.es tablisliment of; a trigger jrarc 147. which causes the revolution :of: ionized specie fromr-trigger ranodei'44,

generally of-coppergor a liker-vaporizable metaLwhich isinjectedintotheinteractionzspacesbetween the parallel 'rodlike el'ectrodesaiausing, the ,Zbreakdo'wm .of the "device,v'similarxtothesbreakdown which occurs upon afusing of the fusible element; alt ,is'l therefore apparent 1 that bygthe-additionof.means forinjecting an electron iion plas'rnaras, for, example gwtrigg'er assembly "41 which may,-for.example,-beanyof the trigger electrodes illustrated inLaffertyIUS. Pat-Nos. 3,394,2'8 l 3,465,192, "and-3,465,205,; ra further: utility may be "found for devices in accord'with'theinvention.--r1x current density fault current.

predetermined value and upon such fusion to' 'sustaiti for one-half cycle of alternating current a fault current greatly in excess of the steady-state current atwhich fusion occurs. Thismay be'done' in accordwith the combination fusible element and rod array "or, other are electrode assemblies of the devices of the invention in :a 50, space which is very small as compared with other-conipetitive devices byutilizing broad area contacts which are not affected by the passage of the high current,low

In addition-to the foregoing, the electrode 'to dev icesin.accord with the present invenftion, provides vacuumfuses' which, 'afterifusion, may be utilized to provide repetitive short-circuiting of soil 'cuitand operatein'tlie triggerable 'arc deyi gm w-r1i1=, by the. foregoing, :the'unique whighrp ower -vacuurn -fuse of-ithe invention "has been disclosed and While'th'e invention 'has been set forth herein with respect :to certain specific embodiments and examples thereof, it is apparent that' m'a'ny modifications and changeswill readily occur to those skilled in the. art. Accordingly, by the appended claims, I intend to cover all suchmoditications and changes asfallwithin the true spiritand'scope of the foregoing disclosure. 1

- What! claim asnew and desire to secure by Letters Patent of the United States is: p v a L 'LHigh power'fuseapparatus comprising:

addition bra trigger tion to like members of said second arc-eleC-I trode assembly to define a plurality of electri-' cally parallel arcing paths;

. A fusible member connected between at least one portion of said first and said second arc electrode assemblies and adapted to disintegrate at a predetermined current and initiate an electric arc between said arc-electrode assemblies; and

d. Means for connecting said arc electrode assemblies in electrical circuit with electrical apparatus to be fused thereby.

2. Fuse apparatus as described in claim 1 wherein each of said are electrode assemblies includes a conductive main member and a plurality of secondary members extending into the volume of said envelope, said secondary members of one of said are electrode members being interleaved with said secondary members of the other'of said arc-electrode assemblies to .disposed main member, and a shield member is' laterally disposed about members.

4.High power fuse apparatus comprising: a. An hermetically sealed envelope evacuated to a pressure of *torr or less;

said interleaved secondary ment is connected between at least one each of respec- I tive rod-like members of of each of said assemblies.

6. Fuse apparatus of claim 5 wherein fusible element is in the form of a ribbon.

7. Fuse apparatus as set forth in claim 4 wherein said fusible element is connected to a plurality of said rodlike members of said assemblies.

Fuse apparatus of claim 4 wherein said fusible member is disposed about said array of rod-like members adjacent the inboard ends of one of said plurality of parallel rod-like members.

9. Fuse apparatus of claim 4 wherein two fusible members are provided encircling said array of rod-like electrode members, one of said fusible elements being disposed adjacent the respective ends of each of said pluralities of rod-like members.

10. Fuse apparatus of claim 4 wherein said fusible I member is in the configuration of a spiral wound about b. first and second arc-electrode assemblies each and providing means for initiating an electric are therebetween upon fusing thereof;

. shield means laterally surrounding said interleaved array and laterally confining arcing specie to an interaction. volume defined by overlapping of and contacting each of said rod-like members within the longitudinal region between the respective inboard ends of said rod-like members of each of said arc-electrode assemblies.

11. Fuse apparatus of claim 4 wherein said fusible member is a metallic member comprising copper.

element is in the form of a wire.

13. Fuse apparatus of claim 4 wherein said arc-electrode assemblies are fabricated of metallic members devoid of sorbed gases and including gases and gasforming constituents to the extent of being capable of sustaining kiloamperes of arcing current for one cycle of powe'rfrequency without the evolution of sufficient gas to raise the measurable pressure within said envelope. Y

14. Fuse apparatus of claim 13 wherein said arc-electrode assemblies are fabricated from OFHC grade copper.

15. Fuse apparatus of claim 13 wherein said arc-electrode assemblies are fabricated from vacuum melted hardened, ductile steel.

16. Fuse apparatus of claim 13 wherein said means for initiating a discharge comprises a trigger assembly for initiating a trigger arc.

17. Fuse apparatus of claim 4 wherein said apparatus further includes means for initiating a discharge within said envelope between said are electrode assemblies by the injection of an ionized plasma thereinto subsequent to fusing of said fusible element and the consumption thereof.

i w w 12. Fuse apparatus of claim 11 wherein said fusible 

1. High power fuse apparatus comprising: a. An hermetically sealed envelope evacuated to a pressure of 10 4 torr or less; b. First and second arc-electrode assemblies each comprising a smooth surfaced array of individual conductive members having a broad area for supporting an electric arc, b1. the individual members of said first arc-electrode assembly being arranged in close disposition to like members of said second arc-electrode assembly to define a plurality of electrically parallel arcing paths; c. A fusible member connected between at least one portion of said first and said second arc electrode assemblies and adapted to disintegrate at a predetermined current and initiate an electric arc between said arc-electrode assemblies; and d. Means for connecting said arc electrode assemblies in electrical circuit with electrical apparatus to be fused thereby.
 2. Fuse apparatus as described in claim 1 wherein each of said arc electrode assemblies includes a conductive main member and a plurality of secondary members extending into the volume of said envelope, said secondary members of one of said arc electrode members being interleaved with said secondary members of the other of said arc-electrode assemblies to provide a plurality of electrically parallel arcing paths over a broad area.
 3. Fuse apparatus of claim 2 wherein said main members of said arc-electrode assemblies are at oppositely disposed ends of said envelope, said secondary members extend generally in the direction of the oppositely disposed main member, and a shield member is laterally disposed about said interleaved secondary members.
 4. High power fuse apparatus comprising: a. An hermetically sealed envelope evacuated to a pressure of 10 4 torr or less; b. first and second arc-electrode assemblies each comprising a plurality of smooth surfaced parallel rod-like arcing members at the same potential with rods of the same assembly, b1. said first and second assemblies interleaved to provide an array of rod-like members in alternating sequence between said assemblies and providing a plurality of electrically parallel large area arcing paths therebetween; c. a fusible member connected between said first and second arc-electrode assemblies making good electrical contact with at least one portion of each and providing means for initiating an electric arc therebetween upon fusing thereof; d. shield means laterally surrounding said interleaved array and laterally confining arcing specie to an interaction volume defined by overlapping of respective rod-like members of said assemblies; e. means for connecting said respective arc electrode assemblies in electrical circuit with electrical apparatus to be fused thereby.
 5. Fuse apparatus of claim 4 wherein said fusible element is connected between at least one each of respective rod-like members of of each of said assemblies.
 6. Fuse apparatus of claim 5 wherein fusible element is in the form of a ribbon.
 7. Fuse apparatus as set forth in claim 4 wherein said fusible element is connected to a plurality of said rod-like members of said assemblies.
 8. Fuse apparatus of claim 4 wherein said fusible member is disposed about said array of rod-like members adjacent the inboard ends of one of said plurality of parallel rod-like members.
 9. Fuse apparatus of claim 4 wherein two fusible members are provided encircling said array of rod-like electrode members, one of said fusible elements being disposed adJacent the respective ends of each of said pluralities of rod-like members.
 10. Fuse apparatus of claim 4 wherein said fusible member is in the configuration of a spiral wound about and contacting each of said rod-like members within the longitudinal region between the respective inboard ends of said rod-like members of each of said arc-electrode assemblies.
 11. Fuse apparatus of claim 4 wherein said fusible member is a metallic member comprising copper.
 12. Fuse apparatus of claim 11 wherein said fusible element is in the form of a wire.
 13. Fuse apparatus of claim 4 wherein said arc-electrode assemblies are fabricated of metallic members devoid of sorbed gases and including gases and gas-forming constituents to the extent of being capable of sustaining 100 kiloamperes of arcing current for one cycle of power frequency without the evolution of sufficient gas to raise the measurable pressure within said envelope.
 14. Fuse apparatus of claim 13 wherein said arc-electrode assemblies are fabricated from OFHC grade copper.
 15. Fuse apparatus of claim 13 wherein said arc-electrode assemblies are fabricated from vacuum melted hardened, ductile steel.
 16. Fuse apparatus of claim 13 wherein said means for initiating a discharge comprises a trigger assembly for initiating a trigger arc.
 17. Fuse apparatus of claim 4 wherein said apparatus further includes means for initiating a discharge within said envelope between said arc electrode assemblies by the injection of an ionized plasma thereinto subsequent to fusing of said fusible element and the consumption thereof. 